1. Field of the Invention
The present invention relates generally to automobile safety systems. More significantly, the present invention relates to a system to allow visual identification of the proper tightness of a fastener.
2. Description of the Prior Art
It is oftentimes necessary in mechanical and industrial environments to have the ability to ascertain whether a given fastener is sufficiently tightened to desired specifications. In this connection, it is necessary to periodically check the tightness of bolts in factories, refineries and processing plants to ensure optimal equipment performance. This need for periodic inspection is a result of vibration common to such environments which may and do cause fasteners to back off over time.
In the automotive environment, drivers of semi-trailers also must periodically check the tightness of wheel lugs to prevent catastrophic accidents. Such a procedure is many times required by insurance carriers and has recently been required by ordinance or otherwise in various countries.
Notwithstanding the insurance and statutory requirements, it is frequently inconvenient to undertake periodic inspection of the fasteners. In this connection, in many industrial applications, the fasteners are used in environments which are hazardous to access due to thermal or chemical constraints. In the automotive application, environmental conditions often render it less than convenient to ensure adequate and proper tightness on all wheels.
One solution proposed to address the above need was prepared in Great Britain Patent Nos. 2,242,720 and 2,325,505 as issued to Marczynski et al. Marczynski employed a system whereby a series of plastic markers were mounted over the top of truck lug bolts so as to form a recognizable pattern. In such a fashion, the truck driver could visually ascertain the current tightness of a given wheel by merely observing the pattern of the markers.
The aforementioned solution presents a number of disadvantages. The first such disadvantage is that the plastic indicators are prone to be dislodged due to the way in which they mount on the lug nut.
A second disadvantage is that the mounting system for the indicators makes them prone to tampering or removal by unauthorized persons since they usually require no more pressure to remove than to affix in the first instance. Yet another disadvantage is that the indicators, due to their construction, are prone to failure in vigorous thermal environments.